154 report — 1859. 



liosauria, Crocodilia , Dinosauria, Lacertilia, Pterosaur ia, Chelonia, Ophidia 

 and Batrachia, which orders were then severally characterized. 



Subsequent researches have brought to light additional forms and struc- 

 tural modifications of cold-blooded air-breathing animals now extinct, which 

 have suggested corresponding modifications of their distribution into ordinal 

 groups. Another result of such deeper insight into the forms that have 

 passed away has been the clearer recognition of the artificiality of the boun- 

 dary between the classes Pisces and Reptilia of modern zoological systems. 



The conformity of pattern in the arrangement of the bones of the out- 

 wardly well-ossified skull in certain fishes with well-developed lung-like air- 

 bladders, e. g. Polypterus, Lepidosteus, Sturio, and in the extinct reptiles Ar- 

 chegosaurus and Labyrinthodon ; — the persistence of the notochord {chorda 

 dorsalis) in Archegosaurus, as in Sturio ; the persistence of the notochord 

 and branchial arches in Archegosaurus and Lepidosiren ; the abseuce of 

 occipital condyle or condyles in Archegosaurus as in Lepidosiren ; the pre- 

 sence of teeth with the labyrinthic interblending of dental tissues in Den- 

 drodus, Lepidosteus, and Archegosaurus, as in Labyrinthodon ; the large 

 median and lateral throat-plates in Archegosaurus, as in Megalichthys, and in 

 the modern fishes Arapaima and Lepidosteus ; — all these characters, as were 

 explained and reasoned upon in my lectures at the Government School of 

 Mines (March, 1858), pointed to one great natural group, remarkable for 

 the extensive gradations of development linking and blending together piscind 

 and reptilian characters within the limits of such group. The salamandroie 

 (or so called 'sauroid') Ganoids, e. g. Lepidosteus and Polypterus, are the 

 most ichthyoid, the Labyrinthodonts are the most sauroid, of this annectent 

 group : the Lepidosiren and Archegosaurus are intermediate gradations, one 

 having more of the piscine, the other more of the reptilian characters. Ar- 

 chegosaurus conducts the march of development from the fish proper to the 

 labyrinthodont type ; Lepidosiren conducts it to the perennibranchiate or mo- 

 dern batrachian type. Both forms expose the artificiality of the ordinary 

 class-distinction between Pisces and Reptilia, and illustrate the naturality of 

 the wider class of cold-blooded vertebrates, which I have called Htematocrya* . 



Reptiles are defined as ' cold-blooded air-breathing vertebrates,' but the 

 Siren and Proteus chiefly breathe by gills, as did, most probably, the 

 Archegosaurus. The modern naked Batrachia annually mature, at once, 

 a large number of small ova ; the embryo is developed with but a small 

 allantoid appendage, and is hatched and excluded with external gills. These 

 are retained throughout life by a few species; the rest undergo a greater or 

 less degree of metamorphosis. Other existing reptiles have comparatively 

 few and large eggs, and the embryo is enclosed in a free amnios and is more 

 or less enveloped by a large allantois; it undergoes no marked transforma- 

 tion after being hatched. 



On this difference, the Batrachia have been, by some naturalists, separated 

 as a distinct class from the Reptilia. But the number of ova simultaneously 

 developed in the viviparous Land Salamanders is much less than in the Siren, 

 and not more than in the Turtle ; and, save in respect of the external gills 

 which disappear before or soon after birth, the Salamander does not undergo 

 a more marked transformation, after being hatched, than does the Turtle or 

 Crocodile t- It depends, therefore, upon the value assigned to the different 

 proportions of the allantois in the embryo of the salamander and lizard, 

 whether they be pronounced to belong, or not, to distinct classes of animals. 



* alfia, blood, Kpvos, cold ; the correlative group is the ' Hcemalotherma.' 

 f The CcEcilia may probably depart still further from the type -batrachian mode of develop- 

 ment, and approach more to the type-reptilian mode. 



